HALIFAX - An arbitrator won't hear constitutional arguments from a Nova Scotia public sector union that is fighting a provincial law to shrink the number of bargaining units for health workers from 50 to four.

The Health Authorities Act is part of a wider merger that also reduces the number of health districts from 10 to two by April 1.

The Nova Scotia Government and General Employees Union had asked arbitrator James Dorsey to rule on whether the law violates Charter provisions guaranteeing rights of association.

In his ruling, Dorsey says he may still consider constitutional arguments from the Canadian Union of Public Employees on the act.